Catalyst system for olefin polymerization

ABSTRACT

It is disclosed a new catalyst system for the polymerization of olefins comprising the product obtainable by contacting the following components: (A) one or more compounds of a late transition metal belonging to Group 8-11 of the Periodic Table; and (B) the reaction product of water with one or more organometallic aluminum compounds of formula (IV): Al(CH 2 —CR 3 R 4 R 5 ) x R 6   y H z , wherein R 3  is a C 1 -C 20  alkyl, C 3 -C 20  cycloalkyl or C 7 -C 20  alkylaryl radical; R 4  is different from a straight alkyl and is a C 3 -C 20  alkyl, C 3 -C 20  cycloalkyl, C 6 -C 20  aryl, C 7 -C 20  alkylaryl or C 7 -C 20  arylalkyl radical; or R 3  and R 4  form together a C 4 -C 6  ring; R 5  is hydrogen or a C 1 -C 20  alkyl, C 6 -C 20  aryl, C 7 -C 20  alkylaryl or arylalkyl radical; R 6  is a C 1 -C 20  alkyl, C 3 -C 20  cycloalkyl, C 6 -C 20  aryl, C 7 -C 20  alkylaryl or C 7 -C 20  arylalkyl radical; x is 1-3; z is 0-1; and y is 3−x−z; the molar ratio between said organometallic aluminum compound and water being comprised between 0.5:1 and 100:1.

FIELD OF THE INVENTION

The present invention relates to new catalyst systems comprising theproduct obtained by contacting late transition metal catalystcompounds,and a specific class of alumoxanes: these catalyst systems areparticularly active and stable in the homo and copolymerization ofolefinic monomers.

PRIOR ART DISCLOSURE

Besides metallocene catalysts based on Groups 4 and 5 of the PeriodicTable of the Elements (new IUPAC notation), the use of late transitionmetal complexes for olefin polymerization has been studied and developedin the last years. These complexes exhibit characteristics differentfrom those of well-known metallocenes, constrained-geometry catalysts ortraditional Ziegler-Natta catalysts, when used in olefin polymerization.L. K. Johnson et al. (J. Am. Chem. Soc. 117:6414-6415, 1995) describesthe use of Ni and Pd complexes with bidentate diimine ligands forα-olefin polymerization; in order to exert a catalytic activity, saidcomplexes are activated with H⁺(OEt₂)₂[B(3,5-(CF₃)₂C₆H₃)₄]⁻,methylalumoxane (MAO) or Et₂AlCl as cocatalysts. These systems have theability to produce highly branched polymers from ethylene and tocopolymerize ethylene with polar monomers.

A class of late transition metal complexes of bidentate α-diimine orβ-diimine ligands is disclosed in the international patent applicationWO 96/23010; said complexes are used in the oligomerization andpolymerization of α-olefins, in particular of ethylene, and in thecopolymerization of ethylene with polar monomers. The complexes areactivated with halo-aluminum alkyl derivatives (such as Et₂AlCl, EtAlCl₂and iBu₂AlCl), MAO and alkylboronic acid derivatives.

The international patent application WO 98/03559 describes thepolymerization of α-olefins or cycloolefins by using one of the above Niand Pd α-diimine complexes, wherein the cocatalyst is a Lewis acidselected from the group consisting of B(C₆F₅)₃, AlCl₃, AlBr₃, Al(OTf)₃and compounds of formula (R^(a)R^(b)R^(c)C)Y, wherein R^(a)-R^(c) arearyl or substituted aryl groups and Y is a relatively non-coordinatinganion. According to this application, compounds commonly used inmetallocene activation such as AlMe₃, AlEt₃, Al(OEt)Et₂ and ZnEt₂ do notexert any cocatalytic activity with diimine Ni and Pd complexes, unlessat least one of the selected cocatalysts is present.

The above-mentioned α-diimine complexes of late transition metals, arealso used in polymerization processes at elevated pressure andtemperatures. thus obtaining polyethylene products having differentmolecular weights and branching degrees (see the international patentapplication WO 97/48737); the catalyst systems are activated with MAO.Bidentate ligands, which are useful in the preparation of Ni complexesactive in the polymerization of ethylene, norbornenes and styrenes, aredescribed in the international patent application WO 97/02298; ascocatalysts are used acids of a non coordinating monoanion of formulaHX, wherein the preferred anions X were BF₄ ⁻, PF₆ ⁻, BAF (i.e.tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) and SbF₆ ⁻; all thepolymerization examples have been carried out in the presence ofHBAF(Et₂O)₂. Further Ni(II) complexes with monoanionic ligands havingdifferent structures are described in the international patentapplication WO 98/30609; said complexes are activated with a Lewis acidcocatalyst, such as BPh₃, B(C₆F₅)₃ or BF₃, or MAO to polymerizea-olefins, cyclopentene, styrene, norbornene or polar monomers.

The international patent applications WO 98/42664 and WO 98/42665describe Group 4-10 metal chelates, and in particular Ni or Pd chelates,comprising bidentate ligand compounds of substituted pyrrolaldimine andsubstituted salicylaldimine. Said chelates are used in catalyst systemsfor olefin homopolymerization or copolymerization with functionalizedα-olefin monomers.

The international patent application WO 98/40374 describes olefinpolymerization catalysts containing Group 8-10 metals and bidentateligands having the following formula:

wherein R is hydrocarbyl, substituted hydrocarbyl or silyl; A and B areheteroatom connected monoradicals wherein the connected heteroatomsbelong to Group 15 or 16, and A and B may be linked by a bridging group.These catalysts optionally contain a Bronsted or Lewis acid ascocatalyst; in the working examples, ethylene oligomerizations or(co)polymerizations are cocatalyzed with MAO. borate compounds, such asHBAr₄ (Ar=3,5-bis(trifluoromethyl)phenyl), B(C₆F₅)₃, and aluminumalkyls, such as Et₂AlCl.

Recently. Brooke L. Small et al. (J. Am. Chem. Soc. 120:4049-4050, 1998)disclosed Fe(II) and Co(II) catalyst systems incorporating tridentatepyridine duimine ligands having the following general structure:

wherein R are H, methyl or iso-propyl. The active catalysts, generatedby the addition of MAO, are able to convert ethylene to linear highdensity polyethylene; increasing the steric bulk of the ortho arylsubstituents increases molecular weight.

The polymerizations of ethylene and propylene with the above-mentionedcomplexes of pyridine bis-imine, and more specifically of2,6-pyridinecarboxaldehyde bis(imines) and 2,6-diacylpyridinebis(imines), are described in the international patent applications WO98/27124 and WO 98/30612 respectively, wherein the above catalysts areactivated by means of the following cocatalysts: methylalumoxane (MAO),boron compounds (such as B(C₆F₅)₃) and aluminum alkyl compounds (such asEt₂AlCl and EtAlCl₂).

Although the above-described late transition metal catalyst systems arevery active in the polymerization of ethylene and may lead to finalpolymers with interesting structural properties, due to the branchingdegree, their use is not completely satisfactory, because of theconsiderable decay of the catalyst activity. In fact, althoughpolymerization activities of these catalysts is quite high in theinitial phase of the polymerization, they rapidly decay in the course ofthe reaction and the deactivation is almost quantitative after fewhours. The deactivation mechanism is not known so far. Therefore, thesecatalysts are not altogether satisfactory if the residence times of thereaction mixture in the reactor are long. This is particularly importantin industrial polymerization processes, where it is not possible tooperate with short residence times.

As will be demonstrated by the same Applicant in the following, aconsiderable polymerization activity decay of these catalyst systemsoccurs in the presence of the cocatalysts tested in the prior artdocuments described above.

Therefore, it is felt the need of lowering the decay rate and thereforeimproving the long-term catalytic activity of the above mentionedpolymerization catalysts, in order to allow their industrialexploitation.

SUMMARY OF THE INVENTION

The Applicant has now unexpectedly found a suitable class of cocatalystsable to activate late transition metal compounds comprising a complex ofa metal of group 8, 9, 10 or 11 of the Periodic Table of the Elements(new IUPAC notation) with a bidentate or tridentate ligand; according tothe present invention, the catalytic activity in olefin polymerizationof the transition metal compounds reported herein can be surprisinglystabilized and therefore enhanced in the long term by adding to thesecatalysts a specific class of alumoxanes of branched alkylaluminumcompounds.

More precisely, the present invention concerns a catalyst system for thepolymerization of olefins comprising the product obtainable bycontacting the following components:

(A) one or more late transition metal compounds having formula (I) or(II):

LMX_(p)X′_(s)  (I)

LMA  (II)

 wherein M is a metal belonging to Group 8, 9, 10 or 11 of the PeriodicTable of the Elements (new IUPAC notation);

L is a bidentate or tridentate ligand of formula (III):

 wherein:

B is a C₁-C₅₀ bridging group linking E¹ and E², optionally containingone or more atoms belonging to Groups 13-17 of the Periodic Table;

E¹ and E², the same or different from each other, are elements belongingto Group 15 or 16 of the Periodic Table and are bonded to said metal M;

the substituents R¹, the same or different from each other, are selectedfrom the group consisting of hydrogen, linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₁-C₂₀ alkyliden, C₃-C₂₀ cycloalkyl, C₆-C₂₀aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionallycontaining one or more atoms belonging to groups 13-17 of the

Periodic Table of the Elements (such as B, Al, Si, Ge, N, P, O, S, F andCl atoms); or two adjacent R¹ substituents form a saturated, unsaturatedor aromatic C₄-C₈ ring, having from 4 to 20 carbon atoms;

m and n are independently 0, 1 or 2, depending on the valence of E¹ andE², so to satisfy the valence number of E¹ and E²; q is the charge ofthe bidentate or tridentate ligand so that the oxidation state ofMX_(p)X′_(s) or MA is satisfied, and the compound (I) or (II) is overallneutral;

the substituents X, the same or different from each other, aremonoanionic sigma ligands selected from the group consisting ofhydrogen, halogen, —R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and —PR₂ groups,wherein the R substituents are linear or branched, saturated orunsaturated, C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containing one ormore atoms belonging to groups 13-17 of the Periodic Table of theElements (new IUPAC notation), such as B, N, P, Al, Si, Ge, O, S and Fatoms; or two X groups form a metallacycle ring containing from 3 to 20carbon atoms; the substituents X are preferably the same;

X′ is a coordinating ligand selected from mono-olefins and neutral Lewisbases wherein the coordinating atom is N, P, O or S;

p is an integer ranging from 0 to 3, so that the final compound (I) or(II) is overall neutral;

s ranges from 0 to 3; A is a π-allyl or a π-benzyl group; and

(B) the reaction product of water with one or more organometallicaluminum compounds of formula (IV):

Al(CH₂—CR³R⁴R⁵)_(x)R⁶ _(y)H_(z)  (IV)

 wherein, in any (CH₂—CR³R⁴R⁵) groups, the same or different from eachother, R³ is a linear or branched, saturated or unsaturated C₁-C₂₀alkyl, C₃-C₂₀ cycloalkyl or C₇-C₂₀ alkylaryl radical, optionallycontaining one or more Si or Ge atoms; R⁴ is a saturated or unsaturatedC₃-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radical, optionally containing one or more Si or Ge atoms,said radical being different from a straight alkyl or alkenyl group; orR³ and R⁴ form together a C₄-C₆ ring; R⁵ is hydrogen or a linear orbranched, saturated or unsaturated C₁-C₂₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or arylalkyl radical, optionally containing one or more Si orGe atoms;

R⁶ is a linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkylradical;

x is an integer ranging from 1 to 3; z is 0 or 1; and y is 3−x−z. themolar ratio between said organometallic aluminum compound and waterbeing comprised between 0.5:1 and 100:1.

The present invention further provides a process for the(co)polymerization of olefins comprising the reaction of polymerizationof one or more olefinic monomers in the presence of a catalyst system asreported above.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst systems for olefin polymerization and the process usingthem, according to the present invention, will be better described inthe following detailed description.

FIGS. 1 and 2 show graphs wherein is plotted the polymerization activityof catalyst systems according to the present invention vs.polymerization time.

FIG. 3 shows a graph wherein the polymerization activity of a prior artcatalyst system is plotted vs. polymerization time.

FIG. 4 shows a graph wherein is plotted the polymerization activity ofcatalyst systems according to the present invention vs. polymerizationtime, compared to that of a prior art catalyst system.

In the late transition metal compound of component (A), having formula(I) or (II):

LMX_(p)X′_(s)  (I)

LMA  (II)

the metal M is preferably selected from the group consisting of Fe, Co,Ni, Pd and Pt. L is a bidentate or tridentate ligand corresponding toformula (III):

wherein B, E¹, E², R¹, m, n and q have the meaning reported above.

According to a preferred embodiment of the present invention, thebridging group B corresponds to a structural formula selected from thegroup consisting of:

wherein G is an element belonging to Group 14 of the Periodic Table, andis preferably C, Si or Ge; r is an integer ranging from 1 to 5; E³ is anelement belonging to Group 16 and E⁴ belongs to Group 13 or 15 of thePeriodic Table;

the substituents R², the same or different from each other, are selectedfrom the group consisting of hydrogen, linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containing one ormore atoms belonging to groups 13-17 of the Periodic Table (such as B,Al, Si, Ge, N, P, O, S, F and Cl atoms); or two R² substituents form asaturated, unsaturated or aromatic C₄-C₈ ring, having from 4 to 20carbon atoms, or they form a polycyclic ring system, optionallycontaining one or more Group 13-16 elements; a substituent R¹ and asubstituent R² may form a substituted or unsubstituted, saturated,unsaturated or aromatic C₄-C₈ ring, having from 4 to 20 carbon atoms andoptionally containing one or more Group 13-16 element. In the bidentateor tridentate ligand L of formula (III), E¹ and E² belong to Group 15 or16 of the Periodic Table, and preferably are selected from the groupconsisting of N, P, O, and S. In the late transition metal compounds offormula (I) or (II), the substituents R¹, the same or different fromeach other, are preferably bulky groups; more preferably, they areC₆-C₂₀ aryl groups, and even more preferably are substituted in the 2and 6 positions with a C₁-C₁₀ alkyl group.

The substituents X are preferably hydrogen, methyl, phenyl, Cl, Br or I;p is preferably 1, 2 or 3.

When X′ is a neutral Lewis base wherein the coordinating atom is N. P, Oor S, it is preferably selected from the group consisting of phosphines,amine, pyridines, nitriles and sulfides; even more preferably, it isselected from the group consisting of triphenylphosphine, tri(C₁-C₆alkyl)phosphines, tricycloalkyl phosphines, diphenyl alkyl phosphines,dialkyl phenyl phosphines, triphenoxyphosphine, trimethylphosphine,pyridine, substituted pyridines, di(C₁-C₃ alkyl) ether andtetrahydrofuran.

When X′ is a mono-olefin, it is a hydrocarbyl group having onecarbon-carbon double bond, having from 2 to 20 carbon atoms; preferablyis a substituted or unsubstituted C₂-C₆ alkene. The variable s ispreferably 0 or 1.

A is a π-allyl or a π-benzyl group. By a π-allyl group is meant amonoanionic ligand with 3 adjacent sp² carbon atoms bound to a metalcenter in an η³ fashion. The three sp² carbon atoms may be substitutedwith other hydrocarbyl groups or functional groups; preferred π-allylradicals are CH₂CHCH₂, CH₂CHCHMe and CH₂CHCMe₂.

By a π-benzyl group is meant a π-allyl ligand in which two of the sp²carbon atoms are part of an aromatic ring; preferred benzyl radicals areCH₂Ph and CH₂C₆F₅.

Examples of other suitable π-allyl and π-benzyl groups can be found inthe international patent application WO 98/30609.

According to a preferred embodiment of the invention, the ligand offormula (III) is bidentate: the bridging group B corresponds tostructural formula B-1, wherein G is C, E¹ and E² are N, m and n are 1and q is 0; said neutral bidentate ligand has formula (V):

wherein R¹ and R² have the meaning reported above.

In formula (V), the substituents R² are preferably the same and areselected from the group consisting of hydrogen, methyl, ethyl, n-propyl,i-propyl and benzyl, or the two substituents R² form together a mono orpolycyclic ring system.

According to a particularly preferred embodiment of the invention, informula (V) the two substituents R² form a acenaphtenquinone group, thusresulting the following ligand:

wherein R¹ has the meaning reported above.

In formula (V), the substituents R¹ are preferably C₆-C₂₀ aryl groups,optionally substituted in the 2 and 6 positions with a C₁-C₁₀ alkylgroup; according to preferred embodiments of the invention, R¹ isselected from the group consisting of phenyl, 2,6-dimethyl-phenyl,2,6-diisopropyl-phenyl and 2,4,6-trimethyl-phenyl.

When the catalyst systems of the invention are used in the production ofhigh molecular polymers, said 2 and 6 positions are preferablysubstituted with a branched C₃-C₂₀ alkyl groups, preferably having asecondary or tertiary carbon atom bonded to the phenyl group.

When the catalyst systems of the invention are used in the production oflow molecular polymers, said 2 and 6 positions are preferablysubstituted with a linear or branched C₁-C₁₀ alkyl group with a primarycarbon atom bonded to the phenyl group.

For macromer preparation, no substituents are present in said 2 and 6positions of the phenyl group.

When the ligand L corresponds to formula (V), M preferably belongs toGroup 10 of the Periodic Table, and even more preferably it is Ni or Pd;if the transition metal compound has formula (I), X radicals arepreferably hydrogen, methyl, Cl, Br or I; p is preferably 2 or 3; s ispreferably 0.

The ligands of formula (V) and the corresponding complexes with latetransition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplication WO 96/23010.

Preferred late transition metal compounds of formula (I), wherein thebidentate ligand L corresponds to formula (V), are reported in thefollowing for illustrative purposes:

[(2,6-iPr₂Ph)—N═C(H)—C(H)═N—(2,6-iPr₂Ph)]NiBr₂

[(2,6-iPr₂Ph)—N═C(Me)—C(Me)═N—(2,6-iPr₂Ph)]NiBr₂

[(2,6-iPr₂Ph)—N═C(An)—C(An)═N—(2,6-iPr₂Ph)]NiBr₂

[(2,6-Me₂Ph)—N═C(H)—C(H)═N—(2,6-Me₂Ph)]NiBr₂

[(2,6-Me₂Ph)—N═C(Me)—C(Me)═N—(2,6-Me₂Ph)]NiBr₂

[(2,6-Me₂Ph)—N═C(An)—C(An)═N—(2,6-Me₂Ph)]NiBr₂

[(2,4,6-Me₃Ph)—N═C(H)—C(H)═N—(2,4,6-Me₃Ph)]NiBr₂

[(2,4,6-Me₃Ph)—N═C(Me)—C(Me)═N—(2,4,6-Me₃Ph)]NiBr₂

[(2,4,6-Me₃Ph)—N═C(An)—C(An)═N—(2,4,6-Me₃Ph)]NiBr₂

or the corresponding dichloride, dimethyl, monochloride or monomethylcomplexes, wherein An=acenaphtenquinone, Me=methyl, iPr=iso-propyl andPh=phenyl.

According to another preferred embodiment of the invention, the ligandof formula (III) is tridentate. B corresponds to the structure B-17wherein the E⁴ is N, E¹ and E² are N, m and n are 1, and q is 0; saidneutral tridentate ligand has formula (VI):

wherein the R¹ and R² groups, the same or different from each other,have the meaning reported above.

According to a particularly preferred embodiment of the invention, inthe tridentate ligand of formula (VI), the substituents R² are hydrogenor methyl, and the substituents R¹ are aryl rings.

When the catalyst systems of the invention are used in the production ofhigh molecular polymers, the substituents R¹ are aryl rings substitutedin the 2 and 6 positions with branched C₃-C₂₀ alkyl groups, having asecondary or tertiary carbon atom bonded to the phenyl group.

When the catalyst systems of the invention are used in the production oflow molecular polymers, the substituents R¹ are aryl rings substitutedin the 2 and 6 positions with linear or branched C₁-C₁₀ alkyl groups,having a primary carbon atom bonded to the phenyl group.

When the tridentate ligand corresponds to formula (VI), the metal Mpreferably belongs to Group 8 or 9 of the Periodic Table, and even morepreferably it is Fe, Ru, Co or Rh; if the transition metal compound hasformula (I), the X radicals, the same or different from each other, arepreferably hydrogen, methyl, Cl Br or I; p is preferably 2 or 3; s ispreferably 0.

The ligands of formula (VI) and the corresponding complexes with latetransition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplications WO 98/27124 and WO 98/30612.

Preferred late transition metal compounds of formula (I), wherein theligand L corresponds to formula (VI), are reported in the following forillustrative purposes:

{2,6-[(2,6-iPr₂Ph)—N═C(Me)]pyridyl}FeBr₂

{2,6-[(2,6-Me₂Ph)—N═C(Me)]pyridyl}FeBr₂

{2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}FeBr₂

{2,6-[(2,6-iPr₂Ph)—N═C(Me)]pyridyl}CoBr₂

{2,6-[(2,6-Me₂Ph)—N═C(Me)]pyridyl}CoBr₂

{2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}CoBr₂

{2,6-[(2,6-iPr₂Ph)—N═C(Me)]pyridyl}FeBr₃

{2,6-[(2,6-Me₂Ph)—N═C(Me)]pyridyl}FeBr₃

{2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}FeBr₃

{2,6-[(2,6-iPr₂Ph)—N═C(Me)]pyridyl}CoBr₃

{2,6-[(2,6-Me₂Ph)—N═C(Me)]pyridyl}CoBr₃

{2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}CoBr₃

or the corresponding chloride complexes (LFeCl₂, LCoCl₂, LFeCl₃ orLCoCl₃, L being one of the ligands reported above) or methyl complexes,wherein Me=methyl, iPr=iso-propyl and Ph=phenyl.

According to another embodiment of the invention, the ligand of formula(III) is bidentate: the bridging group B corresponds to the structuralformula B-3, wherein G is C, E¹ and E² are N, m and n are 2 and q is 0;said neutral bidentate ligand has formula (VII):

wherein R¹ and R² have the meaning reported above.

At least one substituent R¹ linked to each N atom is preferably an arylring, more preferably substituted in the 2 and 6 positions; according topreferred embodiments of the invention, at least one R¹ linked to each Natom is selected from the group consisting of phenyl,2,6-dimethyl-phenyl, 2,6-diisopropyl-phenyl and 2,4,6-trimethyl-phenyl.The remaining R¹ ligand linked to N is preferably hydrogen, methyl orethyl.

The substituents R² are preferably the same and are selected from thegroup consisting of hydrogen, methyl and phenyl, or two substituents R²form together a mono or polycyclic ring system, optionally containingone or more Group 13-16 elements.

When the bidentate ligand corresponds to formula (VII), M is preferablyof Group 10, and even more preferably is Ni or Pd; if the transitionmetal compound has formula (I), X radicals are preferably hydrogen,methyl, Cl, Br or I; p is preferably 2 or 3; s is preferably 0.

The ligands of formula (VII) and the corresponding complexes with latetransition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplication WO 97/02298.

According to another embodiment of the invention, the ligand of formula(III) is bidentate: the bridging group B corresponds to structuralformula B-18, B-19 or B-20, wherein G is C, E¹ and E² are N, m and n are1 and q is 0; said neutral bidentate ligands have formulae (VIII)-(XI):

wherein R¹ and R² have the meaning reported above.

The substituent R¹ are preferably aryl groups, more preferablysubstituted in the 2 and 6 positions; according to preferred embodimentsof the invention, R¹ is selected from the group consisting of phenyl,2,6-dimethyl-phenyl, 2,6-diisopropyl-phenyl and 2,4,6-timenthyl-phenyl.

The substituents R² are preferably the same and are selected from thegroup consisting of hydrogen, methyl and phenyl, or two substituents R²form together a mono or polycyclic ring system, optionally containingone or more Group 13-16 elements; or a substituent R¹ and a substituentR² form together a mono or polycyclic ring system, optionally containingone or more Group 13-16 elements.

When the bidentate ligand corresponds to one of formulae (VIII)-(XI), Mis preferably of Group 10, and even more preferably is Ni(II) or Pd(II);if the transition metal compound has formula (I), X radicals arepreferably hydrogen, methyl, Cl, Br or I; p is preferably 2 or 3; s ispreferably 0.

The ligands of formulae (VIII)-(XI) and the corresponding complexes withlate transition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplication WO 98/40374.

According to another preferred embodiment of the invention, the ligandof formula (III) is bidentate, B corresponds to the structure B-28wherein G is C, E¹ and E² are N, a substituent R¹ and a substituent R²form a substituted ring, m and n are 1, and q is −1; said anionicbidentate ligand has formula (XII):

wherein R¹ and R² have the meaning reported above and R¹⁰-R¹², the sameor different from each other, are selected from the group consisting ofhydrogen, linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkylradicals, optionally containing one or more atoms belonging to groups13-17 of the Periodic Table of the Elements (such as B, Al, Si, Ge, N,P, O, S, F and Cl atoms); or two adjacent substituents R¹⁰-R¹² form asaturated, unsaturated or aromatic C₄-C₈ ring, having from 4 to 40carbon atoms.

According to a particularly preferred embodiment of the invention, inthe bidentate ligand of formula (XII), the substituent R² is hydrogen ormethyl; the substituents R¹ and R¹⁰ are steric bulky groups, preferablyaryl rings (more preferably substituted in the 2 and 6 positions withbranched C₃-C₃₀ alkyl groups) or tertiary C₃-C₆ alkyl groups; thesubstituents R¹¹ and R¹² are preferably hydrogen or methyl.

When the catalyst systems of the invention are used in the production ofhigh molecular and linear polymers, having low degrees of branching, R¹and R¹⁰ are aryl rings substituted in the 2 and 6 positions with abranched C₃-C₁₀ alkyl groups, having a secondary or tertiary carbon atombonded to the phenyl group.

When the catalyst systems of the invention are used in the production oflow molecular polymers or oligomers, R¹ and R¹⁰ are aryl ringssubstituted in the 2 and 6 positions with a linear or branched C₁-C₁₀alkyl group, having a primary carbon atom bonded to the phenyl group.

When the bidentate ligand corresponds to formula (XII), the metal M ispreferably Fe, Co, Rh, Ni or Pd; if the transition metal compound hasformula (I), X radicals, the same or different from each other, arepreferably hydrogen, methyl, Cl Br or I; p is preferably 2 or 3; s ispreferably 0.

The ligands of formula (XII) and the corresponding complexes with latetransition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplication WO 98/42665.

Preferred late transition metal compounds of formula (I), wherein theligand L corresponds to formula (XII), are reported in the following forillustrative purposes:

[C₄H₃N—C(H)═N—(2,6-iPr₂Ph)]NiBr₂

[C₄H₃N—C(Me)═N—(2,6-iPr₂Ph)]NiBr₂

[C₄H₃N—C(H)═N—(2,6-Me₂Ph)]NiBr₂

[C₄H₃N—C(Me)═N—(2,4,6-Me₃Ph)]NiBr₂

or the corresponding dichloride, dimethyl, monochloride or monomethylcomplexes, wherein Me=methyl, iPr=iso-propyl and Ph=phenyl.

According to another preferred embodiment of the invention, the ligandof formula (III) is bidentate, B corresponds to the structure B-12wherein two vicinal substituent R² form an aromatic ring, E¹ and E² areN, m and n are 1, and q is −1; said anionic bidentate ligand has formula(XIII):

wherein R¹ and R² have the meaning reported above; the substituents R¹⁴and R¹⁶, the same or different from each other, are selected from thegroup consisting of hydrogen, linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containing one ormore atoms belonging to groups 13-17 of the Periodic Table of theElements (such as B, Al, Si, Ge, N, P, O, S, F and Cl atoms);

the substituents R¹ and R¹⁵, the same or different from each other, havethe same meaning of substituents R¹⁴ and R¹⁶, optionally forming with anadjacent substituent R¹⁴ or R¹⁶ a saturated, unsaturated or aromaticC₄-C₈ ring, or they are electron withdrawing groups.

According to a particularly preferred embodiment of the invention, inthe bidentate ligand of formula (XIII), the substituents R¹ are stericbulky groups, preferably aryl rings (more preferably substituted in the2 and 6 positions with branched C₃-C₃₀ alkyl groups) or tertiary C₃-C₆alkyl groups; the substituent R² is hydrogen or methyl; the substituentsR¹⁴ and R¹⁶ are hydrogen or methyl; the substituent R¹³ is a stericbulky groups, preferably an aryl ring (more preferably substituted inthe 2 and 6 positions with branched C₃-C₃₀ alkyl groups) or a tertiaryC₃-C₆ alkyl group, or —NO₂, Cl or Br; and R¹⁵ is an electron withdrawinggroup selected from —NO₂, Cl, Br, I, —CF₃, —SO₃ ⁻, —SO₂R and —COO⁻.

When the catalyst systems of the invention are used in the production ofhigh molecular polymers, the substituents R¹ are preferably aryl groupssubstituted in the 2 and 6 positions with a branched C₃-C₃₀ alkylgroups, preferably having a secondary or tertiary carbon atom bonded tothe phenyl group.

When the bidentate ligand corresponds to formula (XIII), the metal M ispreferably Fe, Co, Ni or Pd; if the transition metal compound hasformula (I), X radicals, the same or different from each other, arepreferably hydrogen, methyl, Cl Br or I; p is preferably 2 or 3; s ispreferably 0.

The ligands of formula (XIII) and the corresponding complexes with latetransition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplication WO 98/42664.

According to another preferred embodiment of the invention, the ligandof formula (III) is bidentate, the bridging group B corresponds to thestructural formula B-12, wherein two vicinal substituent R² form anaromatic ring, E¹ is O and E² is N, m=0, n=1, and q is −1; said anionicbidentate ligand has formula (XIV):

wherein R¹, R² and R¹³-R¹⁶ have the meaning reported above in connectionwith formula (XIII).

When the catalyst systems of the invention are used in the production ofhigh molecular polymers, R¹ is preferably an aryl group substituted inthe 2 and 6 positions with a branched C₃-C₂₀ alkyl group, preferablyhaving a secondary or tertiary carbon atom bonded to the phenyl group.

When the bidentate ligand corresponds to formula (XIV), the metal Mpreferably belongs to Group 10 of the Periodic Table, and even morepreferably is Ni; if the transition metal compound has formula (I), Xradicals, the same or different from each other, are preferablyhydrogen, methyl, allyl, Cl, Br or I, p is preferably 1 and s ispreferably 1; if the transition metal compound has formula (II), A ispreferably selected from the group consisting of CH₂CHCH₂, CH₂CHCHMe,CH₂CHCMe₂, CH₂Ph and CH₂C₆F₅ radicals.

Preferred late transition metal compounds of formula (I), wherein theligand L corresponds to formula (XIV), are reported in the following forillustrative purposes:

[{2-O-3-Ph—C₆H₃}—CH═N—(2,6-iPr₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3-(9-anthracenyl)C₆H₃}—CH═N—(2,6-iPr₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3,5-tBu₂—C₆H₂}—CH═N—(2,6-iPr₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3,5-(NO₂)₂—C₆H₂}—CH═N—(2,6-iPr₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3-Ph—C₆H₃}—CH═N—(2,6-iPr₂—C₆H₃)]Ni(C₃H₅)

[{2-O-3-(9-anthracenyl)C₆H₃}—CH═N—(2,6-iPr₂—C₆H₃)]Ni(C₃H₅)

[{2-O-3,5-tBu₂—C₆H₂}—CH═N—(2,6-iPr₂—C₆H₃)]Ni(C₃H₅)

[{2-O-3,5-(NO₂)₂—C₆H₂}—CH═N—(2,6-iPr₂—C₆H₃)]Ni(C₃H₅)

[{2-O-3-Ph—C₆H₃}—CH═N—(2,6-Me₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3-(9-anthracenyl)C₆H₃}—CH═N—(2,6-Me₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3,5-tBu₂—C₆H₂}—CH═N—(2,6-Me₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3,5-(NO₂)₂—C₆H₂}—CH═N—(2,6-Me₂—C₆H₃)]NiPh(PPh₃)

[{2-O-3-Ph—C₆H₃}—CH═N—(2,6-Me₂C₆H₃)]Ni(C₃H₅)

[{2-O-3-(9-anthracenyl)C₆H₃}—CH═N—(2,6-Me₂—C₆H₃)]Ni(C₃H₅)

[{2-O-3,5-tBu₂—C₆H₂}—CH═N—(2,6-Me₂—C₆H₃)]Ni(C₃H₅)

[{2-O-3,5-(NO₂)₂—C₆H₂}—CH═N—(2,6-Me₂—C₆H₃)]Ni(C₃H₅)

wherein Me=methyl, iPr=iso-propyl, tBu=ter-butyl and Ph=phenyl.

The ligands of formula (XIV) and the corresponding complexes with latetransition metals can be prepared according to methods known in thestate of the art, for instance as described in the international patentapplication WO 98/30609 and WO 98/42664.

Component (B) of the catalyst systems according to the present inventionis the reaction product of water with one or more organometallicaluminum compounds of formula (IV):

Al(CH₂—CR³R⁴R⁵)_(x)R⁶ _(y)H_(z)  (IV)

wherein R³, R⁴, R⁵, R⁶, x, y and z have the meaning reported above. Themolar ratio between said organometallic aluminum compound and waterranges from 0.5:1 to 100:1, and preferably from 0.8:1 to 50:1. Aparticularly advantageous value of said molar ratio is about 1:1.

According to the invention, component (B) can be used in combinationwith organometallic aluminum compounds other than those of formula (IV),or in mixture with other compatible cocatalysts known in the state ofthe art.

The substituent R³ is preferably a C₁-C₅ alkyl group, more preferably aC₁-C₃ alkyl group, and even more preferably methyl or ethyl; R⁴ ispreferably a saturated or unsaturated branched-chain C₃-C₂₀ alkyl oralkylaryl group, and more preferably a C₄-C₁₀ alkyl or alkylaryl group,or it is an optionally substituted phenyl group; R⁵ is preferablyhydrogen or a C₁-C₅ alkyl group; R⁶ is preferably a C₁-C₅ alkyl group,and more preferably an isobutyl group.

The above organometallic aluminum compounds can be suitably preparedaccording to the methods known in the state of the art, and preferablyas described in the international patent application WO 96/02580.

A subclass of organometallic aluminum compounds particularlyadvantageous in the catalyst systems according to the present inventioncomprises the compounds of formula (IV) wherein the (CH₂—CR³R⁴R⁵)groups, the same or different from each other, are β,δ-branched groups;said organometallic aluminum compounds correspond to formula (XV):

Al(CH₂—CR³R⁵—CH₂—CR⁷R⁸R⁹)_(x)R⁶ ^(y)H_(z)  (XV)

wherein R⁴, R⁵, R⁶, x, y and z have the meaning reported above;

R⁷ and R⁸, the same or different from each other, are linear orbranched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or alkylaryl groups; the substituents R³and R⁷ and/or R⁷ and R⁸ optionally form one or two rings, having 3 to 6carbon atoms; R⁹ is hydrogen or has the same meaning of R⁷ and R⁸.

Non limiting examples of these compounds aretris(2,4,4-trimethylpentyl)aluminum (TIOA),bis(2,4,4-trimethylpentyl)aluminum hydride,isobutyl-bis(2,4,4-trimethylpentyl)aluminum,diisobutyl-(2,4,4-trimethylpentyl)aluminum,tris(2,4-dimethylheptyl)aluminum and bis(2,4-dimethylheptyl)aluminumhydride.

Another particularly preferred subclass of organometallic aluminumcompounds is constituted by the compounds of formula (IV) wherein the(CH₂—CR³R⁴R⁵) groups, the same or different from each other, areβ,γ-branched groups; therefore, said organometallic aluminum compoundscorrespond to formula (XVI):

Al(CH₂—CR³R⁵—CR⁷R⁸R⁹)_(x)R⁶ _(y)H_(z)  (XVI)

wherein R³, R⁵-R⁹, x, y and z have the meaning reported above forformula (XV).

In said subclass, R³ is preferably a C₁-C₅, more preferably a C₁-C₃alkyl group; according to a preferred embodiment, said R³ is methyl orethyl, R⁵ is preferably hydrogen, R⁷ and R⁸ are preferably C₁-C₅ andmore preferably C₁-C₃ alkyl groups, R⁹ is preferably hydrogen or a C₁-C₅alkyl group, and more preferably a C₁-C₃ alkyl group.

Within this subclass, particularly preferred organometallic aluminumcompounds are:

tris(2,3-dimethyl-butyl)aluminum, tris(2,3,3-trimethyl-butyl)aluminum,tris(2,3-dimethyl-pentyl)aluminum, tris(2,3-dimethyl-hexyl)aluminum,tris(2,3-dimethyl-heptyl)aluminum,tris(2-methyl-3-ethyl-pentyl)aluminum,tris(2-methyl-3-ethyl-hexyl)aluminum,tris(2-methyl-3-ethyl-heptyl)aluminum,tris(2-methyl-3-propyl-hexyl)aluminun,tris(2-ethyl-3-methyl-butyl)aluminum,tris(2-ethyl-3-methyl-pentyl)aluminum, tris(2,3-diethyl-pentyl)aluminum,tris(2-propyl-3-methyl-butyl)aluminum,tris(2-isopropyl-3-methyl-butyl)aluminum,tris(2-isobutyl-3-methyl-pentyl)aluminum,tris(2,3,3-trimethyl-pentyl)aluminum,tris(2,3,3-trimethyl-hexyl)aluminum,tris(2-ethyl-3,3-dimethyl-butyl)aluminum,tris(2-ethyl-3,3-dimethyl-pentyl)aluminum,tris(2-isopropyl-3,3-dimethyl-butyl)aluminum,tris(2-trimethylsilyl-propyl)aluminum,tris(2-methyl-3-phenyl-butyl)aluminun,tris(2-ethyl-3-phenyl-butyl)aluminum,tris(2,3-dimethyl-3-phenyl-butyl)aluminum, tris(1-menthen-9-yl)aluminum

and the corresponding compounds wherein one of the hydrocarbyl groups isreplaced by hydrogen, and those wherein one or two of the hydrocarbylgroups are replaced by an isobutyl group. Particularly preferredcompounds are tris(2,3,3-trimethyl-butyl)aluminum andtris(2,3-dimethyl-butyl)aluminum.

The latter subclass of organoaluminum compounds can be preparedaccording to procedures known in the state of the art, and in particularas described in WO 99/21899 (international patent applicationPCT/EP98/06732).

Another particularly preferred subclass of organometallic aluminumcompounds is constituted by the compounds of formula (IV) wherein the(CH₂—CR³R⁴R⁵) groups, the same or different from each other, bear anaryl group in position β; therefore, said organometallic aluminumcompounds correspond to formula (XVII):

Al[CH₂—C(Ar)R³R⁵]_(x)H_(z)  (XVII)

wherein R³, R⁵, x and z have the meaning reported above, x is 3-z and Aris a substituted or unsubstituted aryl group having from 6 to 20 carbonatoms.

In said subclass, R³ is preferably a C₁-C₅ alkyl group; R⁵ is preferablyhydrogen or a C₁-C₅ alkyl groups; and Ar is preferably selected from thegroup consisting of 4-fluoro-phenyl, 4-chloro-phenyl, 4-methoxyphenyl,4-nitrophenyl, 3-methylphenyl, 3-isopropylphenyl, 2,4-difluorophenyl,2,4-dichlorophenyl, 2,6-difluorophenyl, 2,6-dichlorophenyl,3,5-difluorophenyl, 3,5-dichlorophenyl, 2,4,6-trifluorophenyl,2,4,6-trichlorophenyl, 3,4,5-trifluorophenyl, 3,4,5-trichlorophenyl,pentafluorophenyl and pentachlorophenyl.

Within this subclass, particularly preferred organometallic aluminumcompounds are:

tris(2-phenyl-propyl)aluminium tris[2-(4-fluoro-phenyl)-propyl]aluminiumtris[2-(4-chloro-phenyl)-propyl]aluminium,tris[2-(3-isopropyl-phenyl)propyl]aluminiumtris(2-phenyl-butyl)aluminium tris(3-methyl-2-phenyl-butyl)aluminiumtris(2-phenyl-pentyl)aluminiumtris[2-(pentafluorophenyl)propyl]aluminiumtris[2,2-diphenyl-ethyl]aluminiumtris[2-phenyl-2-methyl-propyl]aluminium and the corresponding compoundswherein one of the hydrocarbyl groups is replaced by hydrogen.

Particularly preferred compounds are tris(2-phenyl-propyl)aluminium,tris[2-(4-fluoro-phenyl)propyl]aluminium andtris[2-(4-chloro-phenyl)propyl]aluminium.

This subclass of organoaluminum compounds can be prepared according toprocedures known in the state of the art, and in particular as describedin WO 01/21674 (corresponding to the European patent application no.99203110.4).

The above-described organometallic aluminum compounds and water can bebrought into contact in different ways. Water can be gradually added tothe alkyl aluminum compound of formula (IV) in solution, in an aliphaticor aromatic inert hydrocarbon solvent such as heptane or toluene;preferably, the compound of formula (IV) is brought into contact withthe wet monomer or solvent in the reactor and component (A), optionallyprecontacted with part of the organometallic aluminum compound, is thenintroduced into the reactor.

According to another embodiment, water can be reacted in combined formas hydrated salt, or it can be absorbed or adsorbed on an inert support,such as silica. According to a further embodiment, the alkyl aluminumcompound (IV) can be allowed to react with boric anhydride or with boricacid.

In the organometallic aluminum compounds of formula (IV), (XV), (XVI)and (XVII), z can be 0 or 1. As it is known in the state of the art,aluminum trialkyls may contain small amounts of bisalkyl-aluminumhydride; the hydride content can slightly change during prolongedstorage periods and depending on the storage temperature. Therefore,component (B) can be a mixture of the two organometallic aluminumcompounds of formula (IV), (XV), (XVI) and/or (XVII) wherein z=0 andz=1, so that the molar ratio between the hydrogen atoms directly boundto aluminum and aluminum atoms (i.e. the overall z value) can be afraction, lower than 1.

The components (A) and (B) of the catalyst system according to thepresent invention can be brought into contact in different manners. Thecatalyst system may be formed prior to its introduction into thereaction vessel, or it may be formed in situ.

The catalyst system may be formed by mixing together components (A) and(B), preferably in solution, in a suitable non-polar solvent such astoluene, benzene, chlorobenzene, an alkane or an alkene, to form aliquid catalyst system. A preferred way of forming the catalyst systemof the invention comprises first mixing components (A) and a part ofcomponent (B), and subsequently adding to the obtained mixture asolution of the rest of component (B), preferably in toluene.

The molar ratio between the aluminum of component (B) and the metal M ofthe compound (A) preferably ranges from 50:1 to 50,000:1, morepreferably from 250:1 to 5000:1, and even more preferably from 500:1 to2,500:1.

The catalysts of the present invention can also be used on inertsupports. This is achieved by depositing the components (A) and/or (B),either singly or in mixture, on inert supports such as silica, alumina,silica/alumina, titania, zirconia, magnesia; suitable inert supports areolefin polymers or prepolymers. The thus obtained supported catalystsystems can be advantageously used in gas-phase polymerization.

The catalyst systems according to the present invention can beconveniently used in polymerization processes, without the occurrence ofthe catalyst deactivation also at prolonged polymerization times. Infact, the Applicant has surprisingly found that the use of component (B)in the catalyst system according to the present invention inhibits themassive deactivation of the catalyst, which is usually observed with thecocatalysts used in the prior art, and above all when MAO is used ascocatalyst; the catalyst systems of the invention allow to obtain highcatalytic activities also in the long term, after several hours ofpolymerization.

Therefore, it is another object of the present invention a process forthe homo-polymerization or co-polymerization of one or more olefinicmonomers, characterized by the fact the polymerization reaction isperformed in the presence of a catalyst system as described above. Saidolefinic monomers are selected from the group consisting of ethylene,C₃-C₂₀ α-olefins, C₄-C₂₀ gem-substituted olefins, C₈-C₂₀ aromaticsubstituted α-olefins, C₄-C₂₀ cyclic olefins, C₄-C₂₀ non conjugateddiolefins and C₂₀-C₁₀₀₀ vinyl and vinylidene terminated macromers.

Moreover, in view of the tolerance of the above-described latetransition metal catalysts to polar monomers, unsaturated polar monomerscan be additionally polymerized or copolymerized. Said preferred polarmonomers include C₄-C₂₀ olefins containing functional groups such asesters, ethers, carboxylates, nitriles, amines, amides, alcohols, halidecarboxylic acids and the like; even more preferably, these polarmonomers are vinyl esters, halides or nitrites.

According to a preferred embodiment, the present invention concerns aprocess for the polymerization of one or more α-olefins of formulaCH₂═CHR, wherein R is hydrogen or a C₁-C₂₀ alkyl, C₅-C₂₀ cycloalkyl orC₆-C₂₀ aryl radical, or the copolymerization of one or more of theseα-olefins with one of the polar monomers reported above. Non limitingexamples of α-olefins which are suitable to be used in thepolymerization process according to the present invention are ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene,4,6-dimethyl-1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene and allylcyclohexane; said α-olefin ispreferably ethylene.

According to a preferred embodiment, the present invention concerns aprocess for ethylene polymerization, performed in the presence of acatalyst system according to the invention wherein, in the latetransition metal compound (A), the ligand L is a bidentate ligand offormula (V), as reported above, and the metal M is Ni or Pd; thepresence of the specific cocatalyst (B), according to the invention,allows to obtain branched polyethylenes, having higher number of totalbranches and lower melting point values in comparison with polyethylenesproduced with the same catalysts, but using MAO as cocatalyst.

The (co)polymerization process according to the present invention can becarried out in the liquid phase or in gas phase; in the former case, itis advantageously carried out in the presence of an inert hydrocarbonsolvent, either aromatic (preferably toluene) or aliphatic (preferablypropane, hexane, heptane, isobutane, isopentane, cyclohexane orisooctane; more preferably isopentane or isooctane).

Alternatively, the (co)polymerization process may be carried out in anolefin solvent. and particularly in a mixture of linear α-olefins and/orhigher branched or internal olefins.

The starting olefinic monomer can be supplied to the reactor togetherwith an inert diluent, such as nitrogen or helium, when the reactant isgaseous, or in a liquid solvent when the reactant is in the liquid form.

The (co)polymerization temperature is preferably comprised between −20°C. and 150° C. more preferably between 10° C. and 100° C., and even morepreferably between 40 and 90° C. The (co)polymerization pressure ispreferably comprised between 100 and 10,000 kPa, more preferably between200 and 8,000 kPa, and even more preferably between 500 and 2,000 kPa.

Reaction times of from 10 minutes to 2 hours have been found to besuitable, depending on the activity of the catalyst system and on thereaction conditions. At the end of the polymerization reaction, aconventional catalyst deactivating agent, such as water, methanol, oranother alcohol, may be added to the reaction mixture, in order toterminate the reaction.

The reaction can be terminated also by introducing air.

The following experimental examples are reported for illustrative andnon limiting purposes.

GENERAL PROCEDURES AND CHARACTERIZATIONS

All the operations with the catalyst systems and the catalyst components(A) and (B) were carried out under nitrogen atmosphere.

Polymerization Solvents

Isooctane (2,4,4-trimethylpentane, 99.8% purity) was dried by prolongednitrogen purge, followed by passage over molecular sieves (water contentof about 1 ppm).

Anhydrous toluene (99.8% purity) from Aldrich was dried over 4 Åmolecular sieves (water content of about 3 ppm).

Ethylene (99.5% purity) was purified over a column containing 4 Åmolecular sieves and BTS catalyst (purchased from BASF) in order toreduce water and oxygen content to <1 ppm.

Intrinsic Viscosity (I.V.): the intrinsic viscosity of the polymers wasmeasured at 135° C. in decaline (data reported in Table 1) or intetrahydronapthalene (THN) (data reported in Table 3).

GPC Analysis: High temperature GPC analyses were performed using thefollowing chromatographic conditions:

Column: PLgel 2 × mixed bed-B, 30 cm, 10 microns Solvent:1,2-dichlorobenzene with antioxidant Flow rate: 1.0 ml/min Temperature:140° C. Detector: refractive index Calibration: polystyrene

DSC Analysis: DSC analyses were performed on a Perkin Elmer DSC7. Thefollowing temperature program was used:

Temp 1: −40° C. Time 1: 3.0 min Rate 1: 15.0° C./min Temp 2: 200° C.Time 2: 3.0 min Rate 2: 15.0° C./min Temp 3: −40° C. Time 3: 3.0 minRate 3: 15.0° C./min Temp 4: 200° C. Time 4: 3.0 min Rate 4: 15.0°C./min Temp 5: −40° C.

The Tm and ΔH values reported in Tables 1 and 2 refer to the secondmelting point Tm2.

Degree of Branching: the total number of branches per 1000 carbon atomswas determined by ¹³C NMR spectroscopy, using 1,2-C₂D₂Cl₄ as solvent,according to the method described in J. Am. Chem. Soc. 120:4049-4050,1998.

CATALYST COMPONENTS

Component (A):

The catalyst [(2,6-iPr₂Ph)—N═C(Me)—C(Me)═N—(2,6-iPr₂Ph)]NiBr₂,corresponding to formula (V), was prepared as described in Example 29 ofWO 96/23010.

The catalyst [(2,6-iPr₂Ph)—N═C(An)—C(An)═N—(2,6-iPr₂Ph)]NiBr₂(An=acenapthenquinone) corresponding to formula (V), was prepared asdescribed in Example 31 of WO 96/23010.

The catalyst {2,6-[(2,6-iPr₂Ph)—N═C(Me)]pyridyl}FeCl₂, corresponding toformula (VI), was prepared as described in Examples 8 of WO 98/27124.

The catalysts {2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}FeCl₂, correspondingto formula (VI), was prepared according to the procedure reported inExample 11 of WO 98/27124, using FeCl₂ instead of CoCl₂.

Component (B):

Tris(2,4,4-trimethyl-pentyl)aluminum (TIOA)

Tris(2,4,4-trimethyl-pentyl)aluminum was prepared according to themethod described in Liebigs Ann. Chem., Volume 629, Ziegler et al.“Aluminiumtrialkyle und Dialkylaluminiumhydride ausAluminiumisobutyl-Verbindungen [Aluminum trialkyls and dialkylaluminiumhydrides from aluminum isobutyl compounds]”, pages 14-19.

(2,4,4-Trimethyl-pentyl)aluminoxane (TIOAO)

(2,4,4-trimethyl-pentyl)aluminoxane used in Examples 1, 3-5, 13-14 and20, and Comp. Ex. 3 was prepared immediately prior to use by reacting a0.45 M toluene solution of tris(2,4,4-trimethyl-pentyl)aluminum (TIOA,prepared as described above) with about a half-equivalent of water. Morespecifically, 3.29 g of TIOA (9.00 mmol) were dissolved in 20 g oftoluene in a bottle with a septum cap. The solution was cooled to 0-4°C. using an ice bath, and 81 ml of water (4.5 mmol) added in four shotsusing a 25 ml syringe, whilst maintaining the temperature below 15° C.and purging the solution with nitrogen. The resulting solution (9.0 mmolTIOAO) was ready to be introduced into the reactor. The cocatalysts usedin Examples 6, 7 and 8 were prepared following the above procedure, byusing a molar ratio of water/TIOA of 0.65:1, 0.70:1 and 0.75:1respectively.

Tris(2,3,3-trimethyl-butyl)aluminum (TTMBA)

Tris(2,3,3-trimethyl-butyl)aluminum was prepared as described in WO99/21899 (international patent application PCT/EP98/06732).

(2,3,3-trimethyl-butyl)aluminoxane (TTMBAO)

(2,3,3-trimethyl-butyl)aluminoxane (TTMBAO) was prepared immediatelyprior to use from the reaction of a 0.45 M toluene solution oftris(2,3,3-trimethyl-butyl)aluminum (TTMBA), prepared as reported above,with about a half-equivalent of water whilst maintaining the reactiontemperature in the range 5-15° C.

(2-Methyl-propyl)aluminoxane (TIBAO)

TIBAO was prepared immediately prior to use by reacting a 0.45 M toluenesolution of TIBA (obtained from Aldrich; catalogue n. 25, 720-6, 1996-7)with a half-equivalent of water, whilst maintaining the reactiontemperature in the range 5-15° C.

Methylalumoxane (MAO)

Methylalumoxane was obtained from Witco as a solution in toluene (4.99%w/w Al).

Tris(2-phenyl-propyl)aluminium—Al(CH₂CHMePh)₃(TPPA)

In a glove box, α-methyl-styrene (283 g, 2.3 mol; Aldrich, dried oversieves) was dissolved in dry toluene (ca. 300 ml) in a 1 L 3-neck flask.Al{CH₂CHMe₂}₃ (TIBA, 100 ml, 0.395 mmol, ex-Witco) was added over 10 minby syringe to the rapidly stirred solution at ambient temperature. Thereaction flask was removed from the glove box and a reflux condenser andnitrogen line attached in the fume hood. The isobutene product wascollected using a graduated collection vessel immersed in a −78° C.acetone/dry ice bath. The reaction mixture was warmed over 90 minutes toan internal temperature of 110.7° C. The reaction was allowed to refluxfor 16 hours (final reflux temperature 126.4° C.), affording ca. 100% ofthe theoretical maximum yield of isobutene (ca. 3.0 equivalents/Al). Theremaining olefin and solvent were removed in vacuo (50° C., 0.05 mbar,90 min) utilizing a dry ice/acetone bath to give 162 g oftris(2-phenyl-propyl)aluminium.

Tris(2-phenyl-propyl)aluminoxane (TPPAO)

Tris(2-phenyl-propyl)aluminoxane (TPPAO) was prepared immediately priorto use from the reaction of a 0.45 M toluene solution oftris(2-phenyl-propyl)aluminium (TPPA) prepared as reported above, with ahalf-equivalent of water whilst maintaining the reaction temperature inthe range 5-15° C. The cocatalysts used in Example 10 was preparedfollowing the above procedure, by using a molar ratio of water/TPPA of0.75:1.

Tris [2-(4-fluoro-phenyl)-propyl]aluminium—Al[CH₂CHMe(4-F—C₆H₄)]₃(TFPPA)

In the glove box, 2-(4-fluoro-phenyl)-propylene (65.1 g, 0.48 mol;Acros, dried over sieves) was dissolved in dry toluene (ca. 70 ml) in a250 ml 3-neck flask. Al{CH₂CHMe₂}₃ (TIBA, 27.9 ml, 0.120 mol, ex-Witco)was added over 10 min by syringe to the rapidly stirred solution. Thereaction flask was removed from the glove box and a reflux condenser andnitrogen line attached in the fume hood. The isobutene product wascollected using a graduated collection vessel immersed in a −78° C.acetone/dry ice bath. The reaction mixture was warmed over 90 minutes toan internal temperature of 119.6° C. The reaction was allowed to refluxfor 16 hours (final reflux temperature 123.5° C.), affording ca. 100% ofthe theoretical maximum yield of isobutene. The remaining olefin andsolvent were removed in vacuo (60° C., 0.05 mbar, 90 min) utilizing adry ice/acetone bath to give 50 g oftris[2-(4-fluoro-phenyl)-propyl]aluminium.

Tris[2-(4-fluoro-phenyl)-propyl]aluminoxane (TFPPAO)

Tris[2-(4-fluoro-phenyl)-propyl]aluminoxane (TFPPAO) was preparedimmediately prior to use from the reaction of a 0.45 M toluene solutionof tris[2-(4-fluoro-phenyl)propyl]aluminium (TFPPA) prepared as reportedabove, with a half-equivalent of water whilst maintaining the reactiontemperature in the range 5-15° C. The cocatalysts used in Example 12 wasprepared following the above procedure, by using a molar ratio ofwater/TFPPA of 0.75:1.

Tris[2-(4-chloro-phenyl)-propyl]aluminium—Al[CH₂CHMe(4-Cl—C₆H₄)]₃(TCPPA)

In the glove box, 2-(4-chloro-phenyl)-propylene (73.2 g, 0.48 mol;Acros, dried over sieves) was dissolved in dry toluene (ca. 80 ml) in a250 ml 3-neck flask. Al{CH₂CHMe₂}₃ (TIBA, 30.0 ml, 0.128 mol, ex-Witco)was added over 10 min by syringe to the rapidly stirred solution. Thereaction flask was removed from the glove box and a reflux condenser andnitrogen line attached in the fume hood. The isobutene product wascollected using a graduated collection vessel immersed in a −78° C.acetone/dry ice bath. The reaction mixture was warmed over 90 minutes toan internal temperature of 123.4° C. The reaction was allowed to refluxfor 18 hours (final reflux temperature 124.4° C.), affording ca. 100% ofthe theoretical maximum yield of isobutene. The remaining olefin andsolvent were removed in vacuo (60° C., 0.05 mbar, 90 min) utilizing adry ice/acetone bath to give 69 g oftris[2-(4-chloro-phenyl)-propyl]aluminium.

Tris[2-(4-chloro-phenyl)-propyl]aluminoxane (TCPPAO)

Tris[2-(4-chloro-phenyl)-propyl]aluminoxane (TCPPAO) was preparedimmediately prior to use from the reaction of a 0.45 M toluene solutionof tris[2-(4-chloro-phenyl)propyl]aluminium (TCPPA) prepared as reportedabove, with a half-equivalent of water whilst maintaining the reactiontemperature in the range 5-15° C. The cocatalysts used in Example 16 wasprepared following the above procedure, by using a molar ratio ofwater/TCPPA of 0.75:1.

Tris(2-ethyl-3-methyl-butyl)aluminium (TEMBA)

Tris(2-ethyl-3-methyl-butyl)aluminium was prepared as described in WO99/21899 (international patent application PCT/EP98/06732).

Tris(2-ethyl-3-methyl-butyl)aluminoxane (TEMBAO)

Tris(2-ethyl-3-methyl-butyl)aluminoxane (TEMBAO) was preparedimmediately prior to use from the reaction of a 0.45 M toluene solutionof Tris(2-ethyl-3-methyl-butyl)aluminium (TEMBA) prepared as reportedabove, with about a half-equivalent of water whilst maintaining thereaction temperature in the range 5-15° C.

CATALYST SYSTEM PREPARATION

Catalyst systems preparation was generally carried out by premixing thecatalyst (component (A)) and the cocatalyst (component (B)) in 15 mltoluene at room temperature and maintaining the mixture under stirringfor a maximum of 2 hours. The obtained solution was then usedimmediately in the polymerization reaction. In some cases, the solutionof the catalyst component (A) was injected directly into the reactorcontaining the cocatalyst.

POLYMERIZATION TRIALS EXAMPLES 1-2 AND COMPARATIVE EXAMPLES 1-3

A 5 liter reactor equipped with turbine stirrer, steam/water temperaturecontrol and a catalyst injection system was heated to 150-160° C.overnight. whilst purging with nitrogen. cooled and then pickled at 70°C. using a mixture of TIBA (0.25 g), toluene (20 mL) and propylene (500g). The pickle mixture was removed and the reactor was purged withnitrogen several times. The reactor was then charged with 2.5 Lisooctane whilst increasing the temperature from 20 to 50° C. and addingethylene to a total pressure of 7.5 bar. The total pressure was keptconstant throughout the polymerization by feeding ethylene.

A cocatalytic solution prepared as described above, containing 9.0 mmolTIOAO, was introduced into the reactor using an injection system, washedin using 20 g of toluene.

Meanwhile {2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}FeCl₂ (22.9 μmol) wasmixed with 22.88 g of a toluene solution containing 3.294 g TIOAO (9.0mmol). Ten minutes after the introduction of the 9.0 mmol of TIOAO intothe reactor, 4.995 g (5.00 μmol) of the solution of the activated ironcompound (aged for 1 h; having the Al/Fe premix ratio reported inTable 1) was injected into the reactor (using 20 mL toluene), containingthe Al/Fe ratio reported in Table 1. The polymerization was continuedfor 1 hour at a constant temperature of 50° C., using 840-1100 rpmstirring.

The polymerization was then stopped by injection of 5-10 mL methanol.The heating was then discontinued and the ethylene rapidly vented andthe slurry polyethylene was precipitated with methanol and collected.The polyethylene fractions were dried (70-80° C., 200 mbar, nitrogenpurge) and combined to give the total yield of polyethylene.

The reaction conditions as well as polymerization yields andcharacterization data of the obtained polymers are indicated in Table 1.

In Example 2, ethylene polymerization was performed according to asimilar procedure with TTMBAO as cocatalyst. In Comparative Examples 1and 2 ethylene polymerization was performed according to a similarprocedure with MAO and TIBAO, respectively, as cocatalysts. InComparative Examples 3 ethylene polymerization was performed accordingto a similar procedure, using TIOA in the premixing step and TIOAO inthe autoclave.

For these experiments, the reaction conditions, as well aspolymerization yields and I.V. of the obtained polymers, are indicatedin Table 1.

The obtained data demonstrate that the catalyst systems according to thepresent invention are able to give polymerization activities comparableor even superior to the ones obtained with other cocatalysts known inthe state of the art. For instance, the use of the prior art cocatalystTIBAO in Comparative Example 2 showed a significantly lower activitycompared to Examples 1 and 2, wherein components (B) were used,according to the present invention.

FIGS. 1 to 3 report the kinetic profiles of the polymerization reactionscarried our in Example 1, Example 2 and Comparative Example 1respectively, wherein the catalyst polymerization activity (measured asmonomer consumption) is plotted as a function of time (polymerizationsstart at time=10 minutes); the plots were obtained by determining thequantity (g) of ethylene consumption at time intervals of 15 seconds.

FIG. 3 shows that, when MAO is used as cocatalyst, a pronounced catalystdeactivation occurs during the initial phase of the polymerization, asis evident from the ethylene consumption pattern; initial ethyleneconsumption is very rapid, whereas after approximately 15 minutespolymerization proceeds at a much slower rate. Therefore, when MAO isused, although the initial activity is high, a significant catalystdeactivation takes place after 10-15 minutes of polymerization.

In contrast, the presence of one or more components (B) according to thepresent invention totally inhibits the catalyst deactivation; in FIGS. 1and 2 no significant catalyst decay is observed after more than 1 hour,as evident from the fact that ethylene consumption does not change withtime.

Finally, Comparative Example 3 demonstrates that, contrarily to theteaching of the prior art, the use of an aluminum alkyl as premixingagent, such as TIOA, leads to the complete deactivation of the catalystsystem. Unexpectedly, this does not happen by using the alumoxane ofTIOA, as demonstrated in example 1.

EXAMPLES 3 AND 4

Ethylene was polymerized according to the procedure of Example 1, withthe only difference that two different cocatalysts were used in thepreparation of the catalyst system and in the polymerization reaction,respectively. Reaction conditions, polymerization yields and the I.V. ofthe obtained polymers are reported in Table 1.

EXAMPLES 5-12 AND COMPARATIVE EXAMPLE 4

In Example 5, a 2.35 liter reactor equipped with an anchor stirrer,steam/water temperature control and a catalyst injection system washeated to 150-160° C. overnight, whilst purging with nitrogen, cooledand then pickled at 70° C. using a mixture of TIBA (0.25 g), toluene (20mL) and isooctane (500 g). The pickle mixture was removed and thereactor was purged with nitrogen several times. The reactor was thencharged with 1.25 L isooctane, whilst increasing the temperature from 20to 50° C. and adding ethylene to a total pressure of 7.5 bar. The totalpressure was kept constant throughout the polymerization by feedingethylene.

A cocatalytic solution prepared as described above, containing 2.0 mmolTIOAO (prepared, as described above. using a 0.5:1 molar ratio of waterand TIOA), was introduced into the reactor using an injection system,washed in using 20 g of toluene.

Meanwhile {2,6-[(2,4,6-Me₃Ph)—N═C(Me)]pyridyl}FeCl₂ (16.0 μmol) wasmixed with 15.60 g of a toluene solution containing 2.23 g TIOAO (6.1mmol). Ten minutes after the introduction of the 2.0 mmol of TIOAO intothe reactor, 0.985 g (1.00 μmol) of the solution of the activated ironcompound (aged for 15 min; having the Al/Fe premix ratio reported inTable 1) was injected into the reactor (using 20 mL toluene), containingthe Al/Fe ratio reported in Table 1. The polymerization was continuedfor 1 hour at a constant temperature of 50° C., using 840-1100 rpmstirring.

The polymerization was then stopped by injection of 5-10 mL methanol.The heating was then discontinued and the ethylene rapidly vented andthe slurry polyethylene was precipitated with methanol and collected.The polyethylene fractions were dried (70-80° C., 200 mbar, nitrogenpurge) and combined to give the total yield of polyethylene.

The reaction conditions, polymerization yields and characterization dataof the obtained polymers are indicated in Table 1.

In Example 6-8, ethylene polymerization was performed according to theprocedure of Example 5, but TIOAO was prepared using the ratios of waterto TIOA given in Table 1.

In Examples 9 and 10, ethylene polymerization was performed according tothe procedure of Example 5, using TPPAO instead of TIOAO, with thewater/TPPA ratio given in Table 1; the amounts of the catalystscomponents used are reported in Table 1.

In Examples 11 and 12, ethylene polymerization was performed accordingto the procedure of Example 5, using TFPPAO instead of TIOAO, with thewater/TFPPA ratio given in Table 1; the amounts of the catalystcomponents used are reported in Table 1.

In Comparative Example 4, ethylene polymerization was performedaccording to the procedure to Example 5, using MAO instead of TIOAO ascocatalyst, and using the amounts of catalyst components reported inTable 1.

For these experiments, the reaction conditions, polymerization yieldsand characterization data of the obtained polymers are indicated inTable 1.

EXAMPLE 13 AND COMPARATIVE EXAMPLE 5

Ethylene was polymerized according to the procedure of Example 1, withthe difference that [(2,6-iPr₂Ph)—N═C(Me)—C(Me)═N—(2,6-iPr₂Ph)]NiBr₂ wasused as the catalyst; moreover, in Comparative Example 5, MAO was usedas cocatalyst instead of TIOAO.

Reaction conditions and polymerization yields of the obtained polymersare reported in Table 2.

The obtained results demonstrate that the catalyst systems according tothe invention show polymerization activities comparable to the onesobtained when MAO is used as cocatalyst.

EXAMPLE 14

In Example 14, ethylene polymerization was performed according to theprocedure of Example 13, but using[(2,6-iPr₂Ph)—N═C(An)—C(An)═N—(2,6-iPr₂Ph)]NiBr₂ (An=acenapthenquinone)as catalyst and TIOAO as cocatalyst. Reaction conditions, polymerizationyields and characterization data of the obtained polymers are reportedin Table 2.

EXAMPLES 15-19 AND COMPARATIVE EXAMPLE 6

In the following examples, no catalyst premixing step was carried out inthe polymerization procedure.

In Example 15, a 5 liter reactor was pickled and then charged with 2.5 Lisooctane, as described in Example 1, and ethylene was added to a totalpressure of 7.8 bar. A cocatalytic solution, prepared as describedabove, containing 3.0 mmol TCPPAO, was introduced into the reactor usingan injection system, washed in using 20 g of toluene. Meanwhile[(2,6-iPr₂Ph)—N═C(An)—C(An)═N—(2,6-iPr₂Ph)]NiBr₂ (An=acenapthenquinone)(22.9 μmol) was dissolved in 10.03 g of toluene. Ten minutes after theintroduction of the TCPPAO into the reactor, 2.579 g (5.00 μmol) of thesolution of the iron compound were injected into the reactor (using 20mL toluene), resulting in the Al/Fe ratio reported in Table 2. Thepolymerization was continued for 1 hour at a constant temperature of 50°C, using 840-1100 rpm stirring.

The polymerization was then stopped by injection of 5-10 mL methanol.The heating was then discontinued and the ethylene rapidly vented andthe polyethylene product isolated by solvent removal. The polymer wasdried (70-80° C., 200 mbar, nitrogen purge) and combined to give thetotal yield of polyethylene.

The reaction conditions as well as polymerization yields and polymercharacterization data are indicated in Table 2.

In Example 16, ethylene polymerization was performed according to theprocedure of Example 15, wherein TCPPAO was prepared with thewater/TCPPA ratio given in Table 2.

In Example 17, ethylene polymerization was performed according to theprocedure of Example 15, using TFPPAO as cocatalyst instead of TCPPAO.

In Example 18, ethylene polymerization was performed according to theprocedure of Example 15, using TTMBAO as cocatalyst instead of TCPPAO.

In Example 19, ethylene polymerization was performed according to theprocedure of Example 15, using TEMBAO as cocatalyst instead of TCPPAO.

In Comparative Example 6, ethylene polymerization was performedaccording to the procedure of Example 15, using MAO as cocatalysts.

For these experiments, the reaction conditions, as well aspolymerization yields and characterization data of the obtained polymersare indicated in Table 2.

FIG. 4 reports the kinetic profiles of the polymerization reactionscarried our in Examples 15 and 17 and Comparative Example 6respectively, wherein the catalyst polymerization activity (measured asmonomer consumption) is plotted as a function of time (polymerizationsstart at time=0 minutes); the plots were obtained by determining thequantity (g) of ethylene consumed at time intervals of 15 seconds.

FIG. 4 shows that, when MAO is used as cocatalyst (Comp. Ex. 6), apronounced catalyst deactivation occurs during the initial phase of thepolymerization, as is evident from the ethylene consumption pattern;initial ethylene consumption is very rapid, whereas after approximately15 minutes polymerization proceeds at a much slower rate. Therefore,when MAO is used, although the initial activity is high, a significantcatalyst deactivation takes place after 10-15 minutes of polymerization.In contrast, the presence of one or more components (B) according to thepresent invention inhibits the catalyst deactivation; in FIG. 4 verylittle catalyst decay is observed after more than 1 hour for Ex. 15 and17.

Moreover, from the data reported in Table 2, it is evident that thecatalyst systems of the present invention allow to obtain polyethyleneshaving a higher number of total branches with respect to polymers thatare obtainable with catalyst systems containing conventionalcocatalysts, such as MAO; in fact, in Examples 15-19, catalyst systemscontaining components (B) of the invention afford polyethylenes having anumber of total branches equal to 67-71 brances/1000 carbon atoms, i.e.much higher than 57.5 branches/1000C, obtained using MAO as cocatalyst(see Comp. Ex. 6).

In line with the above branching tendency, the polyethylenes obtained bymeans of the catalyst systems of the invention show melting pointsvalues much lower than the one of Comp. Ex. 6.

EXAMPLE 20 AND COMPARATIVE EXAMPLES 7-8

A 200 mL glass autoclave, provided with magnetic stirrer, temperatureindicator and feeding line for ethylene, was purified and fluxed withethylene at 35° C. At room temperature were introduced 90 ml of hexane.

The catalytic system was prepared separately in 10 ml of hexane byconsecutively introducing TIOAO (Al/H₂O=2.1), TIOA or MAO and, after 5minutes under stirring, the amount of{2,6-[(2,6-iPr₂Ph)—N═C(Me)]pyridyl}FeCl₂ reported in Table 3, dissolvedin the lowest possible amount of toluene.

After 5 minutes under stirring, the solution was introduced into theautoclave under ethylene flow; the reactor was closed and thetemperature risen to 50° C. The autoclave was then pressurized to 4.6barg and the total pressure was kept constant by feeding ethylene.

After 10 minutes, the reaction was stopped by cooling and degassing thereactor, and by introducing 1 ml MeOH. The obtained polymer was washedwith acidic MeOH, the with MeOH and finally dried under vacuum in ovenat 60° C.

The polymerization conditions, the obtained yields and IV data areindicated in Table 3.

From the results reported in Table 3, it is evident that the catalystsystems according to the present invention are unexpectedly as active asthe ones known in the state of the art, using MAO as cocatalyst.Unexpectedly, the use of an aluminum alkyl such as TIOA is completelyinactive in olefin polymerization, as demonstrated in ComparativeExample 8.

TABLE 1 Al/M Al/M Catalyst Cocatalyst premix Cocatalyst reactor H₂O/AlTime Yield Activity I.V. M_(w)/ Tm ΔH Example micromol premix mol/molReactor mol/mol mol/mol min g_(PE) Kg_(PE)/g_(M) · h dl/g M_(w) × 10⁻³M_(n) ° C. J/g Ex. 1 5.0 TIOAO 393 TIOAO 1800 0.50 60 66.0 236 1.37 91.79.00 n.d. n.d. Ex. 2 5.0 TTMBAO 366 TTMBAO 1800 0.50 65 82.7 273 1.71226.0 13.1 n.d. n.d. Comp. Ex. 1 0.2 MAO 380 MAO 1800 0.50 60 60.8 54432.05 n.d. n.d. n.d. n.d. Comp. Ex. 2 22.9 TIBAO 393 TIBAO 393 0.50 6533.4 24 3.7 n.d. n.d. n.d. n.d. Comp. Ex. 3 22.9 TIOA 1500 TIOAO 3930.50 60 0.0 0 Ex. 3 0.2 MAO 380 TIOAO 1800 0.50 51 23.7 2500 2.33 n.d.n.d. n.d. n.d. Ex. 4 5.0 TIOAO 440 MAO 1800 65 31.7 100 2.84 n.d. n.d.n.d. n.d. Ex. 5 1.0 TIOAO 380 TIOAO 2000 0.50 60 53.0 949 n.d. 88.0 7.9n.d. n.d. Ex. 6 0.2 TIOAO 380 TIOAO 10000 0.65 60 11.0 985 n.d. 38.5 3.7132.5 229.7 Ex. 7 0.2 TIOAO 380 TIOAO 10000 0.70 60 41.0 3671 n.d. 51.94.7 134.5 234.5 Ex. 8 0.2 TIOAO 380 TIOAO 10000 0.75 60 88.0 7878 n.d.183.0 13.2 134.0 231.0 Ex. 9 5.0 TPPAO 380 TPPAO 400 0.50 60 51.9 186n.d. 84.7 12.1 135.0 230.6 Ex. 10 0.6 TPPAO 380 TPPAO 3330 0.75 60 64.01910 n.d. n.d. n.d. n.d. n.d. Ex. 11 0.4 TFPPAO 380 TFPPAO 5000 0.50 6033.0 1477 n.d. n.d. n.d. 133.9 233.7 Ex. 12 0.3 TFPPAO 380 TFPPAO 66670.75 60 50.5 3014 n.d. n.d. n.d. n.d. n.d. Comp. Ex. 4 0.1 MAO 380 MAO20000 67 62.5 10022 n.d. 243.5 16.0 139.0 231.0

TABLE 2 Al/M Al/M Activity Catalyst Cocatalyst premix Cocatalyst reactorH₂O/Al Time Yield Kg_(PE)/ ΔH Branches/ Tm Example micromol premixmol/mol Reactor mol/mol mol/mol min g_(PE) g_(M) · h J/g M_(w) × 10⁻³M_(w)/M_(n) 1000 C ° C. Ex. 13  (1) 14.3 TIOAO 353 TIOAO 632 0.50 5529.9 39 n.d. n.d. n.d. n.d. n.d. Comp. Ex. 5  (1) 14.2 MAO 1500  MAO 63250 28.9 42 n.d. n.d. n.d. n.d. n.d. Ex. 14 (2) 5.0 TIOAO 380 TIOAO 12000.50 60 7.0 24 11.5 215.5 2.2 n.d. 43.9 Ex. 15 (2) 5.0 — — TCPPAO 6000.50 60 39.9 136 35.2 n.d. n.d. 70.3 39.5 Ex. 16 (2) 5.0 — — TCPPAO 6000.75 60 35.8 122 33.8 n.d. n.d. 67.0 42.4 Ex. 17 (2) 5.0 — — TFPPAO 6000.50 60 35.0 119 31.4 n.d. n.d. 71.0 38.6 Ex. 18 (2) 5.0 — — TTMBAO 6000.50 60 14.0 48 35.8 n.d. n.d. 67.3 42.5 Ex. 19 (2) 5.0 — — TEMBAO 6000.50 60 18.0 61 36.9 n.d. n.d. 68.4 42.5 Comp. Ex. 6 (2) 5.0 — — MAO 60060 46.8 159 45.6 289.5 2.3 57.5 57.3 (1)[(2,6-iPr2Ph)—N═C(Me)—C(Me)═N-(2,6-iPr2Ph)]NiBr2 (2)[(2,6-iPr2Ph)—N═C(An)—C(An)═N-(2,6-iPr2Ph)]NiBr2 (An =acenapthenequinone)

TABLE 3 Catalyst Cocatalyst Al/Fe Yield PE Activity I.V. Example(micromol) Cocatalyst (mmol) (mol/mol) (g) (kgPE/g_(Fe) · h) (dl/g) Ex.20 0.16 TIOAO 0.168 1020 1.39 933 1.59 Comp. Ex. 7 0.16 TIOA 0.175 10650.00 0.00 — Comp. Ex. 8 0.20 MAO 0.216 1095 1.79 962 3.01

What is claimed is:
 1. A catalyst system for the polymerization ofolefins comprising the product obtained by contacting the followingcomponents: (A) one or more late transition metal compounds havingformula (I) or (II): LMX_(p)X′_(s)  (I) LMA  (II)  wherein M is a metalbelonging to Group 8, 9, 10 or 11 of the Periodic Table of the Elements;L is a bidentate or tridentate ligand of formula (III):

 wherein: B is a C₁-C₅₀ bridging group linking E¹ and E², optionallycontaining one or more atoms belonging to Groups 13-17 of the PeriodicTable; E¹ and E², the same or different from each other, are elementsbelonging to Group 15 or 16 of the Periodic Table and are bonded to saidmetal M; the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₁-C₂₀ alkyliden, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals,optionally containing one or more atoms belonging to groups 13-17 of thePeriodic Table; or two adjacent R¹ substituents form a saturated,unsaturated or aromatic C₄-C₈ ring, having from 4 to 20 carbon atoms; mand n are independently 0, 1 or 2, so to satisfy the valence number ofE¹ and E²; q is the charge of the bidentate or tridentate ligand so thatthe oxidation state of MX_(p)X′_(s) or MA is satisfied, the compound (I)or (II) being overall neutral; the substituents X, the same or differentfrom each other, are monoanionic sigma ligands selected from the groupconsisting of hydrogen, halogen, —R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and—PR₂ groups, wherein the R substituents are linear or branched,saturated or unsaturated, C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containing oneor more atoms belonging to groups 13-17 of the Periodic Table; or two Xgroups form a metallacycle ring containing from 3 to 20 carbon atoms; X′is a coordinating ligand selected from mono-olefins and neutral Lewisbases wherein the coordinating atom is N, P, O or S; p is an integerranging from 0 to 3; s ranges from 0 to 3; A is a π-allyl or a π-benzylgroup; and (B) the reaction product of water with one or moreorganometallic aluminum compounds of formula (IV): Al(CH₂—CR³R⁴R⁵)_(x)R⁶_(y)H_(z)  (IV)  wherein in any (CH₂—CR³R⁴R⁵) groups, the same ordifferent from each other, R³ is a linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl or C₇-C₂₀ alkylaryl radical,optionally containing one or more Si or Ge atoms; R⁴ is a saturated orunsaturated C₃-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radical, optionally containing one or moreSi or Ge atoms, said radical being different from a straight alkyl oralkenyl group; or R³ and R⁴ form together a C₄-C₆ ring; R⁵ is hydrogenor a linear or branched, saturated or unsaturated C₁-C₂₀ alkyl, C₆-C₂₀aryl, C₇-C₂₀ alkylaryl or arylalkyl radical, optionally containing oneor more Si or Ge atoms; R⁶ is a linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radical; x is an integer ranging from 1 to3; z is 0 or 1; and y is 3−x−z, the molar ratio between saidorganometallic aluminum compound and water being comprised between 0.5:1and 100:1.
 2. The catalyst system according to claim 1, characterized inthat, in the transition metal compound of formula (I) or (II), saidmetal M is selected from the group consisting of Fe, Co, Rh, Ni, Pd andPt.
 3. The catalyst system according to claim 1, characterized in that,in the ligand L of formula (III), said bridging group B corresponds to astructural formula selected from the group consisting of:

wherein G is an element belonging to Group 14 of the Periodic Table; ris an integer ranging from 1 to 5; E³ is an element belonging to Group16 and E⁴ is an element belonging to Group 13 or 15 of the PeriodicTable; the substituents R², the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containingone or more atoms belonging to groups 13-17 of the Periodic Table; ortwo R² substituents form a saturated, unsaturated or aromatic C₄-C₈ring, having from 4 to 20 carbon atoms, or they form a polycyclic ringsystem, optionally containing one or more Group 13-16 elements; asubstituent R¹ and a substituent R² optionally form a substituted orunsubstituted, saturated, unsaturated or aromatic C₄-C₈ ring, havingfrom 4 to 20 carbon atoms and optionally containing one or more Group13-16 element.
 4. The catalyst system according to claim 1,characterized in that, in the ligand L of formula (III), E¹ and E² areselected from the group consisting of N, P, O and S.
 5. The catalystsystem according to claim 1, characterized in that, in the ligand L offormula (III), the substituents R¹ are C₆-C₂₀ aryl groups, substitutedin the 2 and 6 positions with a C₁-C₁₀ alkyl group.
 6. The catalystsystem according to claim 1, characterized in that, in the transitionmetal compound of formula (I), X is selected from the group consistingof hydrogen, methyl, phenyl, Cl, Br and I, and X′ is selected from thegroup consisting of triphenylphosphine, tri(C₁-C₆ alkyl)phosphines,tricycloalkyl phosphines, diphenyl alkyl phosphines, dialkyl phenylphosphines, triphenoxyphosphine, trimethylphosphine, pyridine,substituted pyridines, di(C₁-C₃ alkyl) ether and tetrahydrofurane. 7.The catalyst system according to claim 1, characterized in that, in thetransition metal compound of formula (II), A is a π-allyl or a π-benzylgroup selected from the group consisting of CH₂CHCH₂, CH₂CHCHMe,CH₂CHCMe₂, CH₂Ph and CH₂C₆F₅ radicals.
 8. The catalyst system accordingto claim 3, characterized in that: in the ligand of formula (III), thebridging group B corresponds to structural formula B-1, wherein G is C,E¹ and E² are N, m and n are 1 and q is 0, said ligand having formula(V):

wherein the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₁-C₂₀ alkyliden, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals,optionally containing one or more atoms belonging to groups 13-17 of thePeriodic Table; R² has the meaning reported in claim 3; and said metal Mis Ni or Pd.
 9. The catalyst system according to claim 8, characterizedin that the substituents R¹ are C₆-C₂₀ aryl groups, optionallysubstituted in the 2 and 6 positions with a C₁-C₁₀ alkyl group; and thesubstituents R² are selected from the group consisting of hydrogen,methyl, ethyl, n-propyl, i-propyl and benzyl, or the substituents R²form together a mono or polycyclic ring system.
 10. The catalyst systemaccording to claim 3, characterized in that: in the ligand of formula(III), B corresponds to the structure B-17 wherein the E⁴ is N, E¹ andE² are N, m and n are 1, and q is 0, said ligand having formula (VI):

wherein the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₁-C₂₀ alkyliden, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals,optionally containing one or more atoms belonging to groups 13-17 of thePeriodic Table; R² has the meaning reported in claim 3; and said metal Mis selected from the group consisting of Fe, Ru, Co and Rh.
 11. Thecatalyst system according to claim 10, characterized in that thesubstituents R¹ are C₆-C₂₀ aryl groups, optionally substituted in the 2and 6 positions with a C₁-C₁₀ alkyl group; and the substituents R² arehydrogen or methyl.
 12. The catalyst system according to claim 1,characterized in that, in component (B), the molar ratio between saidorganometallic aluminum compound and water ranges from 0.8:1 to 50:1.13. The catalyst system according to claim 1, characterized in that, informula (IV), R³ is a C₁-C₅ alkyl group; R⁴ is a branched-chain C₃-C₂₀alkyl or alkylaryl group; R⁵ is hydrogen or a C₁-C₅ alkyl group; and R⁶is a C₁-C₅ alkyl group.
 14. The catalyst system according to claim 1,characterized in that, in component (B), said organometallic aluminumcompound has formula (XV): Al(CH₂—CR³R⁵—CH₂—CR⁷R⁸R⁹)_(x)R⁶_(y)H_(z)  (XV) wherein R³, R⁵, R⁶, x, y and z have the meaning reportedin claim 1; R⁷ and R⁸, the same or different from each other, are linearor branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or alkylaryl groups; the substituents R³and R⁷ or R⁷ and R⁸ optionally form one or two rings, having 3 to 6carbon atoms; R⁹ is hydrogen or has the same meaning of R⁷ and R³. 15.The catalyst system according to claim 14, characterized in that saidorganometallic aluminum compound is selected from the group consistingof tris(2,4,4-trimethylpentyl)aluminumbis(2,4,4-trimethylpentyl)aluminum hydride,isobutyl-bis(2,4,4-trimethylpentyl)aluminum,diisobutyl-(2,4,4-trimethylpentyl)aluminum,tris(2,4-dimethylheptyl)aluminum and bis(2,4-dimethylheptyl)aluminumhydride.
 16. The catalyst system according to claim 1, characterized inthat, in component (B), said organometallic aluminum compound hasformula (XVI): Al(CH₂—CR³R⁵—CR⁷R⁸R⁹)_(x)R⁶ _(y)H_(z)  (XVI) wherein R³,R⁵, R⁶, x, y and z have the meaning reported in claim 1; R⁷ and R⁸, thesame or different from each other, are linear or branched, saturated orunsaturated C₁-C₂₀ alkyl, C₃C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or alkylaryl groups; the substituents R³ and R⁷ or R⁷ and R⁸optionally form one or two rings, having 3 to 6 carbon atoms; R⁹ ishydrogen or has the same meaning of R⁷ and R⁸.
 17. The catalyst systemaccording to claim 16, characterized in that said organometallicaluminum compound is selected from the group consisting of:tris(2,3-dimethyl-butyl)aluminum, tris(2,3,3-trimethyl-butyl)aluminum,tris(2,3-dimethyl-pentyl)aluminum, tris(2,3-dimethyl-hexyl)aluminum,tris(2,3-dimethyl-heptyl)aluminum,tris(2-methyl-3-ethyl-pentyl)aluminum,tris(2-methyl-3-ethyl-hexyl)aluminum,tris(2-methyl-3-ethyl-heptyl)aluminum,tris(2-methyl-3-propyl-hexyl)aluminum,tris(2-ethyl-3-methyl-butyl)aluminum,tris(2-ethyl-3-methyl-pentyl)aluminum, tris(2,3-diethyl-pentyl)aluminum,tris(2-propyl-3-methyl-butyl)aluminum,tris(2-isopropyl-3-methyl-butyl)aluminum,tris(2-isobutyl-3-methyl-pentyl)aluminum,tris(2,3-trimethyl-pentyl)aluminum, tris(2,3,3-trimethyl-hexyl)aluminum,tris(2-ethyl-3,3-dimethyl-butyl)aluminum,tris(2-ethyl-3,3-dimethyl-pentyl)aluminum,tris(2-isopropyl-3,3-dimethylbutyl)aluminum,tris(2-trimethylsilyl-propyl)aluminum,tris(2-methyl-3-phenyl-butyl)aluminum,tris(2-ethyl-3-phenyl-butyl)aluminum,tris(2,3-dimethyl-3-phenyl-butyl)aluminum, tris(1-menthen-9-yl)aluminumand the corresponding compounds wherein one of the hydrocarbyl groups isreplaced by hydrogen and those wherein one or more of the hydrocarbylgroups are replaced by an isobutyl group.
 18. The catalyst systemaccording to claim 1, characterized in that, in component (B), saidorganometallic aluminum compound has formula (XVII):Al[CH₂—C(Ar)R³R⁵]_(x)H_(z)  (XVII) wherein R³, R⁵, x and z have themeaning reported in claim 1 and Ar is a substituted or unsubstitutedaryl group having from 6 to 20 carbon atoms.
 19. The catalyst systemaccording to claim 18, characterized in that said organometallicaluminum compound is selected from the group consisting of:tris(2-phenyl-propyl)aluminium tris[2-(4-fluoro-phenyl)-propyl]aluminiumtris[2-(4-chloro-phenyl)-propyl]aluminium,tris[2-(3-isopropyl-phenyl)-propyl]aluminiumtris(2-phenyl-butyl)aluminium tris(3-methyl-2-phenyl-butyl)aluminiumtris(2-phenyl-pentyl)aluminiumtris[2-(pentafluorophenyl)-propyl]aluminiumtris[2,2-diphenyl-ethyl]aluminiumtris[2-phenyl-2-methyl-propyl]aluminium and the corresponding compoundswherein one of the hydrocarbyl groups is replaced by hydrogen.
 20. Aprocess for the homo-polymerization or co-polymerization of one or moreolefinic monomers, wherein the polymerization reaction is performed inthe presence of a catalyst system as claimed in claim
 1. 21. The processaccording to claim 20, characterized in that said olefinic monomer isselected from the group consisting of ethylene, C₃-C₂₀ α-olefins, C₄-C₂₀gem-substituted olefins, C₈-C₂₀ aromatic substituted α-olefins, C₄-C₂₀cyclic olefins, C₄-C₂₀ non conjugated diolefins and C₂₀-C₁₀₀₀ vinyl andvinylidene terminated macromers.
 22. The process according to claim 21,characterized in that said α-olefin has formula CH₂═CHR, wherein R ishydrogen or a C₁-C₂₀ alkyl, C₅-C₂₀ cycloalkyl or C₆-C₂₀ aryl radical.23. The process according to claim 20, characterized in that saidolefinic monomer is a polar C₄-C₂₀ olefin, containing one or morefunctional groups selected from the group consisting of esters, ethers,carboxylates, nitrites, amines, amides, alcohols, halide and carboxylicacids.